Offshore drilling on the continental shelves is progressing into deeper and deeper waters, and therefore, frequently requires subsea wellheads and floating drilling equipment. The technology surrounding offshore drilling is well developed. However, no practical equipment is presently available to the industry for the purpose of regaining the control of an abandoned wellhead on the seabed after the same has erupted and is spilling formation fluids into the sea. The environmental pollution caused by such outpouring of formation liquids and gases can have disastrous consequences, as witnessed the recent pollution created over a large section of the Gulf of Mexico and adjacent beaches by the erupted well off the coast of Mexico.
Typically, an oil or gas well erupts during its initial drilling. After losing control of the well, the floating drilling rig abandons the well being drilled as quickly as possible to avoid harm to its personnel and injury to its equipment. Generally, however, the subsea blowout preventer stack and the subsea wellhead remain, even though one or both may be in damaged condition. In this abandoned condition, oil and gas continue to flow through the wellhead, the well formation, or the well casing. The spill forms a so-called "plume". Usually the plume has its apex at the top of the blowout preventer stack. The plume has a conical shape whose base is at the sea surface and covers a relatively large and increasing area. With the hydrocarbon fluids on the sea surface, conditions are ripe for a fire to erupt. Usually, the fire erupts before the floating drilling rig has a chance to disconnect and run away from the drilling site. Techniques have been developed for the drilling rig to put such a fire out and to continue with the emergency evacuation procedures.
The objects of the invention are to move over the plume, as soon as possible, with an emergency well-control vessel, which is equipped to prevent re-ignition of the plume, to use its special equipment and trained personnel to gain control of the abandoned well, and to stop as quickly as possible the polluting flow of hydrocarbon fluids into the water body of the sea.